CIA director John Brennan said that militants of the so-called ’Islamic State of Iraq and the Levant’ (ISIL) takfiri group have used chemical weapons and have the capability to make small quantities of chlorine and mustard gas.

CIA director John Brennan said that militants of the so-called 'Islamic State of Iraq and the Levant' (ISIL) takfiri group have used chemical weapons and have the capability to make small quantities of chlorine and mustard gas, CBS News reported Thursday.

"We have a number of instances where ISIL has used chemical munitions on the battlefield," Brennan told CBS News, which released excerpts of an interview to air in full on the "60 Minutes" news program on Sunday.

The network added that he told "60 Minutes" the CIA believes that ISIL has the ability to make small amounts of mustard or chlorine gas for weapons.

"There are reports that ISIS [ISIL] has access to chemical precursors and munitions that they can use," Brennan said.

Brennan also warned of the possibility that ISIL could seek to export the weapons to the West for financial gain.

"I think there's always the potential for that. This is why it's so important to cut off the various transportation routes and smuggling routes that they have used," he said.

The release of the interview excerpts comes two days after similar comments from spy chief James Clapper before a congressional committee.

"ISIL has also used toxic chemicals in Iraq and Syria, including the blister agent sulfur mustard," Clapper, the director of national intelligence, told lawmakers on Tuesday.

He said it was the first time an extremist group had produced and used a chemical warfare agent in an attack since Japan's Aum Supreme Truth cult carried out a sarin attack during rush hour in the Tokyo subway in 1995.

The Organization for the Prohibition of Chemical Weapons (OPCW) - which oversaw the dangerous removal and elimination of Syria's avowed stockpile - now says that declared arsenal has been completely destroyed.

Last year, officials in the autonomous Iraqi region of Kurdistan said blood tests had shown that ISIL militants used mustard agent in an attack on Kurdish peshmerga forces in August.

At the time of the attack, The Wall Street Journal cited US officials as saying they believed ISIL had used mustard agent.